fix(Color correction): Display default value in slider to match the radio button

The default value for display in the radio buttons were hard-coded and was not
being reflected to the slider correctly.

Bug: 359379399
Test: locally tested + unit tests added
Flag: com.android.server.accessibility.enable_color_correction_saturation

Change-Id: I95bd0ae1d32561dbbf6b4e87efe70595c9566de8